The long-term objective of this application is to elucidate the influence of psychological factors on immune functioning in humans. The goal of this proposal is to examine the the possible influence of classical conditioning on measures of immune competence in breast cancer patients receiving cycles of chemotherapy. Chemotherapy drugs have two common side effects - nausea and immunosuppression. Previous reports have indicated that experience with chemotherapy can condition patients so that simply returning to the hospital, environment induces nausea and vomiting. The proposal will examine the possibility that patients may also develop conditioned changes in immune function. In vitro measures of immune competence will be assessed in peripheral blood obtained in the patient's home (baseline) and in the hospital prior to chemotherapy (i.e., in the presence of the putative conditional stimuli). The proposed research will thus explore the possible clinical relevance of classica conditioned changes in immune response that have previously been demonstrated in experimental animals. Specific aims are: 1. To determine whether breast cancer patients receiving adjuvant chemotherapy develop conditioned immune suppression; 2. To investigate factors that might influence development of conditioned immunopression in these chemotherapy patients; 3. To explore possible physiological mechanisms that may be responsible for the conditioned immune suppression.